Thursday, February 9, 2012

The Mysterious Epigenome by Thomas Woodward and James Gills

The Human Genome Project was a great success in advancing our knowledge of DNA, but nearly a decade later, the scientists are finding out there is much more to the story.

Scientists are now finding a complex system instructing DNA called the epigenome. (from the Greek, epi, having the nuance of “over” or “above.”) “The epigenome refers to the entire coordinated system of 'control information' that resides above and beyond the bare DNA sequences.” (54) The authors liken the epigenome to the director of the DNA orchestra.

The authors focus on two areas: the latest news from the world of DNA, and how science stumbled upon the control system of our DNA. The theme of human health is emphasized throughout the book.

The authors reveal the complexity of the cell. The E. coli, about two-millionths of a meter, has DNA with about 4.5 million pairs, 4.5 megabytes of information with over four thousand files. Human DNA? 3.1 billion letter-pairs, the equivalent of 14,000 books of 250 pages each. Some plants have even more, such as the Paris japonica, having the record at 149 billion letters per cell. Even a species of wheat has five times as much DNA as the human cell.

But the biggest surprise? The record is held by a single-cell species, Polychaos dubium, with about 670 billion letters of DNA. And Darwin knew nothing of it.

What is the role of the eipgenome system? Its central function is to control the expression of DNA. But the picture is not complete. Research on the epigenome is accelerating, and scientists around the world are delving into both the molecular structure and the functional roles of the epigenome's sections and layers.” (69) The methyl tags seems to silence that gene. Other tags and proteins seems to determine of the DNA is “locked” away or open for use. Histone tags are thought to also work as triggers, signals or switches to the DNA.

One ongoing mystery has been how a stem cell, specifically, a fertilized human egg cell, can differentiate into all the types of tissues in the body. The epigenome has been shown to be the key. In the developmental stages, each cell is directed to its unique use of the DNA files by the epigenetic system.

Each human carries some two hundred versions of the epigenome. The diversity is needed because humans have at least that many cell types (blood, skin, nerve, bone, etc.). “It is now clear that each cell type has a unique set of epigenetic software, whose instructions are tailored precisely for that cell.” (74) Unlike DNA, mapping the epigenome would mean doing so for more than two hundred different informational systems. (The first step in the process has begun.)

The authors use the image of the DNA molecule being a massive filing cabinet. “In that cabinet are tens of thousands of master blueprint files (genes), from which duplicate copies can be made (RNAs), which are then sent to the machine shop, where skilled workers produce a myriad of tools and building parts (the proteins). Under the direction of the chief engineer [epigenome], these molecules interact in intricate ways to produce every form of life.” (76)

With over two hundred different versions of the epigenome, how did they become established in the first place? Or, how do two hundred epithegenetic directors unfurl from a single fertilized egg cell? Somehow, the epigenome knows how to direct the stem cell to produce dozens of different types of tissue. But what system directs the rewriting of the epigenetic system itself?

Some scientists suggest the DNA rewrites the epigenome when needed and then the epigenome in turn directs the DNA in new ways, producing new cell types. (A little circular...)

When the zygote is poised for cell division, the structural goal, whether human or whale, is somehow contained within the cell. It is not the DNA alone that contains the building plans, some argue.

The authors conclude their book with and investigation into the relationship between the epigenome and evidence for a creator. They note that the epigenome “overflows with examples of irreducible complexity...” (114) I'll let you read the book and find the rest of their evidence. You'll also find information on the relationship of the epigenome and DNA to Darwinism. Overlapping messages in some genes caused one scientist to declare that their existence is “virtually impossible by chance.” (123) You'll also find out that pseudogenes have a function after all.

In the end, the authors report, “Thus, a reasonable conclusion is that an intelligent being was the source of life.” (141) Whether you agree or not, you might want to read this book before you make up your mind for good.

This book is an excellent introduction to the ongoing studies of the complexity of the cell.

Thomas Woodward, PhD, is a professor at Trinity College of Florida. He is the author of two books about Darwin. He is founder and director of the C. S. Lewis Society, and lectures in universities on scientific, apologetic, and religious topics.

James Gills, MD, is founder and medical director of the St. Luke's Cataract & Laser Institute in Tarpon Springs, Florida.

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I am a retired Christian bookstore owner of 33 years. I still love books and read as many as I can, blogging my reviews. I have also taken up photography and sell photos of Whidbey Island and nearby landscapes.